The present invention relates to an optical filter and an imaging device including the same.
Imaging devices such as cameras use a CMOS sensor to convert incident light into electronic signals, thereby forming images. To realize high-quality images with the high pixel counts of the cameras, newly developed back side illuminated-type (BSI-type) CMOS sensors have been applied to main cameras instead of front side illuminated-type (FSI-type) CMOS sensors widely used in the related art. The FSI-type CMOS sensors have an effect of blocking out some of light since wirings are formed on a top surface of a photodiode (PD). On the other hand, the BSI-type CMOS sensors may receive a larger amount of incident light, compared to the FSI-type CMOS sensors, since the wirings are disposed under the photodiode to receive a larger amount of light, and thus have an effect of increasing the intensity of an image by 70% or more. Therefore, the BSI-type CMOS sensors have generally been applied to most cameras with over eight million pixels.
Such BSI-type CMOS sensors have a structure in which light having a larger angle of incidence can also reach the photodiode, compared to those of the FSI-type CMOS sensors.
In general, the CMOS sensors may also detect light in a wavelength region which cannot be seen with the naked eye. Since an image is distorted by the light in such a wavelength region, colors different from those seen with the naked eye are observed. To solve this problem, an optical filter is used in the front of the CMOS sensors. However, the conventional optical filter has a problem in that the transmission spectrum of the optical filter varies as the angle of incidence of light varies, thereby resulting in distorted images.